1. Field of the Invention
This invention relates to a moving picture camera with an adjustable rotary shutter. The adjustable rotary shutter having a rotary shutter and a shutter adjusting blade which adjusting blade can be adjusted coaxially to the rotary shutter, and which adjusting blade is connected by means of a transmission with a positioning motor coupled to the shaft of the rotary shutter, and to an arrangement for the operation of such an adjustable rotary shutter.
2. Background Information
Federal Republic of Germany laid open Patent Application Number DE-OS 29 47 333 discloses an adjustable rotary shutter for a moving picture camera of the type described above, which has a shutter adjusting sector oriented coaxially on the rotation shaft of the rotary shutter. The shutter adjusting sector can be adjusted by means of an adjusting shaft mounted so that it can rotate in the rotation shaft of the rotary shutter. One end of the adjusting shaft is connected to a positioning motor placed on the rotation shaft of the rotary shutter, while the other end has a pinion which is connected via a transmission to the shutter adjusting sector.
The adjustable rotary shutter of the prior art makes possible a continuous adjustment of the aperture when the rotary shutter is in motion, by feeding the positioning motor with a voltage whose polarity specifies the direction of the adjustment. The fact that the rotary shutter can be adjusted during movement guarantees that the aperture of the shutter rotates synchronously and in correct phase with the film transport mechanism, covers the image area during the film transport phase, and is not smaller than the operating angle which the corresponding film feed mechanism allows. Then the exposure of the moving picture image takes place when the film is standing still in the vicinity of the remaining shutter bright sector, so that a reduction of this bright sector reduces the exposure time available, while an enlargement of the bright sector provides a longer exposure time. With a continuously adjustable rotary shutter, therefore, the exposure time based on a specified exposure program or other parameters can be adjusted to the current lighting conditions or the desired effects.
The current shutter adjusting sector is measured in the adjustable rotary shutter of the prior art by means of an electro-optical scanning device and an electronic control system, and consists of a luminous source located in the movement path of the adjustable rotary shutter and an opto-receiver, which together form a photoelectric barrier for the determination of the actual opening times of the adjustable rotary shutter. By means of a digital circuit, the light pulses emitted by the photoelectric barrier are counted, and the position of the shutter adjusting sector or the value of the aperture is determined from the count. For this reason, the measurement of the shutter adjusting sector is possible only when the adjustable rotary shutter is in motion. To maintain the desired shutter adjusting sector, it is also necessary to constantly readjust the positioning motor, to maintain the desired and specified shutter adjusting sector.
U.S. Pat. No. 4,322,140 discloses an adjustable rotary shutter for moving picture cameras which consists of several shutter blades which can be moved in relation to one another, and which are located on a shutter shaft, which is connected by means of a transmission to a film transport motor. A hollow shutter shaft sleeved over on the shutter shaft is connected by means of an adjusting cylinder to a positioning motor, which rotates the shutter blades in relation to one another. The hollow shutter shaft has a pin engaged in a hole of the one external shutter blade, while the other external shutter blade has a hole into which a pin of the transmission connected to the film transport motor is engaged. The shutter blades have radial grooves which extend over a specified angle, so that the individual shutter blades can be adjusted in relation to one another over a specified total angle.
The position of the adjusting cylinder and thus of the shutter blades in relation to one another is detected by means of several switches which are arranged on the periphery of the adjustment cylinder and are engaged with cams located on the adjustment cylinder. Thus, as a whole, the shutter aperture angle can be detected when the moving picture camera is in operation, but when the camera is not operating, measurement is possible only within a broad tolerance range.